QK18-1油田注水开发储层损害研究

Research on Reservoir Damage of Water Flooding in QK18-1 Oilfield

QK18-1油田沙河街组油藏注水开发近20年,目前75%以上的油井欠注,油田经济效率低。为明确储层损害机理、建立提高油田注水井吸水能力的有效方法,通过室内静态配伍性实验、水敏性评价实验和水质调研结果,结合铸体薄片和电子显微镜照片对比了探井和开发井储层岩心的微观地质特征,分析了该油田注水困难的原因。结果表明,储层损害的关键因素是混合污水与地层水不配伍形成粒径为10~30μm的CaCO_3垢,在储层中呈菱面体、自形程度高的CaCO_3垢晶呈颗粒状分布在孔隙中及喉道处导致储层物性降低;混合污水矿化度低,回注引发水敏损害。水处理系统悬浮物含量超标也是影响注水效果的重要因素。针对油田注水开发中储层损害问题,提出了预防措施和建议,以提高注水井吸水能力,保证油田注采平衡。

The history of oil reservoir waterflooding development in Shahejie formation of QK18-1 oilfield was nearly 20 years. At present, more than 75% of the oil wells were lack of injection, and the economic efficiency of oilfield was low. In order to define the mechanism of reservoir damage and establish an effective method to improve the injectivity of oilfield injection wells, the micro geological features between exploration well and development well reservoir cores were compared and the reason of injection difficulty in this oilfield was analyzed through static compatibility test, water sensitivity experiment, water quality survey, combining the photos of casting thin section and electron microscope. The results showed that the key factor of oil reservoir damage was the formation of CaCO3 with 10-30 μm particle size as a result of the incompatibility between mixed waste water and formation water. The CaCO3 fouling in the reservoir was a rhombohedral body with good euhedral degree. The crystal grain distributed in the pore and throat, which resulted in the decrease of reservoir physical property. The salinity of mixed waste water was low, and the re-injection led to water sensitive damage. The excess content of suspended matter in water treatment system was also an important factor which influenced the water injection effect. Aiming at the damage problem of reservoir during oilfield water flooding, precaution and suggestions were put forward to improve the water intake capacity of water injection well and ensure the balance between injection and production of oilfield.